Illinois-based Mennie's Machine Co, manufacturer of machined castings and forgings, now uses robotic automation to meet its customers' stringent demands for speed and quality. Human limitations had prevented Mennie's from achieving throughput and consistency requirements for a major contract to manufacture automotive drive shaft components for sport utility vehicles and full size trucks. In addition, the company had to deal with safety and ergonomic issues for employees due to repetitive activities. Consequently, frequent employee absences made production planning nearly impossible.
Operating three shifts per day, the company used a manual operation for one year before it determined that automation was needed. The manual system, which typically yielded 80 pieces per hour, did not achieve Mennie's production goals of 118 pieces per hour.
"We realized that in order to position ourselves as a world class manufacturer, we needed to implement leading-edge technology," says Mennie's vice-president, Bill Mennie. "On this project, speed and quality were the highest priorities, because when it comes to automotive manufacturing there is no margin for error."
According to Mennie, production complexity was another key factor in the decision to go with robotics. In addition to the many different processes and types of machinery involved in the production of finished parts, the company was challenged to balance cycle times between each process. With manual operation, it became difficult to overcome bottlenecks in the system.
Mennie's selected Fanuc Robotics North America for a turnkey solution because of the company's reputation for delivering reliable products and systems expertise. In addition, Mennie's appreciated having a supplier within close proximity to its manufacturing facility. Although Fanuc Robotics is headquartered near Detroit, its full-service facility (located just outside of Chicago) took complete responsibility for the design, build, installation, and service of the system.
Mennie's has a system design philosophy of "factory within a factory." This means that they need a series of robotic workcells linked through a common part transfer conveyor. "Fanuc Robotics understood what we were trying to accomplish and encouraged an atmosphere of teamwork," says Mennie.
The fully automated system incorporates nine material handling robot models. Mennie's provided the pallets, part fixtures, safety fencing, conveyor equipment, PLC hardware, and other peripherals. Each robot is equipped with HandlingTool and Collision Guard software, custom grippers, and a control interface to the equipment and conveyor. The HandlingTool software package provides built-in functions, menu-driven prompts, and point-and-shoot position teaching, making it easy for operators to create and run programs. Collision Guard allows a robot to sense a potential collision along any axis and stops robot operation in time to minimize damage to the end-of-arm-tooling, the part, or the robot.
The entire system consists of 10 consecutive processes linked via conveyor. Raw parts are first manually loaded into a "face and center" machine before being conveyed downstream through nine automated machining processes. At each "stop" along the conveyor, parts are automatically loaded and unloaded by robots. First, an M-6i, capable of lifting up to 13.2 lb, picks raw parts and places them into a CNC lathe for machining. The robot then places finished parts onto a part pallet that is located on the conveyor. Next, each full part pallet makes its way to an LR Mate 100i tabletop model robot, which loads and unloads parts into and out of a small broach machine. In the next process, another M-6i alternately loads and unloads parts onto one of two fixtures of a large broach machine for further processing. A third M-6i moves parts into and out of a boring operation.
In the final processes, an S-430iF, which can lift up to 286 lb, sequentially loads and unloads parts into and out of four machines that perform various groove and ream operations. Following this operation, parts are loaded and unloaded by a fourth M-6i robot to and from a drilling operation, then conveyed to another LR Mate 100i for a spline roll machining process. Next, an M-16i robot, capable of lifting up to 35 pounds, handles parts two at a time into a heat-treat operation. Finally, a fifth M-6i is used to load and unload parts for grinding.
At Mennie's, production quality is assessed by tracking scrap dollars. During final inspection, each part attribute is examined for dimensional tolerance and cosmetic appearance. Rejects are tagged and then further evaluated to determine how to eliminate inaccuracy. Robotic automation has contributed to a reduction in scrap rates. As a result of the robotic system, Mennie's has experienced significant competitive advantages, including:
- accurate and consistent part loading
- a reduction in part defects
- increased productivity (typically 120 pieces per hour)
- improved control of the entire manufacturing system
- less cost per piece
- flexibility to meet future production demands.
The close working relationship between Mennie's and Fanuc Robotics is a major factor in the success of the project. "Our expectations were met and responsibilities were understood without experiencing any unexpected surprises," says Mennie. "I credit open and honest customer/supplier communication for that." Another contributing factor to the successful system was the commitment that Mennie's had to using automation to achieve its goals. "We put our trust in Fanuc Robotics' engineering team to supply a turnkey solution that would help us achieve our vision of 'factory within a factory' and they didn't let us down," says Mennie.
Production is humming at Mennie's. The three-shift operation is running at 95% uptime, a 15% increase over the previous manual operation. In fact, Mennie's estimates that the robotic system has helped the company reduce total production costs by approximately 25%. Robotic automation has also helped Mennie's increase production flexibility. Not only is the system expandable to accommodate additional machines, but (with slight modifications to fixtures) it could easily accommodate new part designs. Mennie's can switch to manual production during routine preventive maintenance. Since the original robotic cells were installed in 1997, Mennie's has expanded the system twice, including the purchase of an additional robot for a drilling operation and an additional machine tool to increase throughput in a turning operation.
